Extended Forecast Discussion NWS Weather Prediction Center College Park MD 300 AM EDT Mon Jul 09 2018 Valid 12Z Thu Jul 12 2018 - 12Z Mon Jul 16 2018 ...Pattern overview/Guidance evaluation/Preferences with weather highlights... Latest models and ensembles this evening show better than average agreement on the evolution of the synoptic pattern across North America through the medium range period. A mid- and upper-level trough lifting out of the Northeast will bring another shot of cool air into the Northeast late this week while playing a key role in steering Tropical Cyclone Chris northeastward at some distance off the New England coast on Thursday. The UKMET continues to be the outlier by bringing the storm very close to New England. This scenario is considered to be of low probability. Consult NHC products for latest information on Chris. Meanwhile, a subtropical high will anchor itself over the central Plains late this week as a couple of mid-latitude shortwave troughs move across western Canada just north of the U.S.-Canadian border. Models agree that the first shortwave will bring a cold front across the northern Plains into the Great Lakes where thunderstorms could become strong Wednesday and Thursday. Another front is forecast to form in the Pacific Northwest and then move into the northern Plains in the weekend with scattered showers and thunderstorms. From the southeastern U.S. westward along the Gulf Coast, a dissipating front will keep a good chance of showers and thunderstorms in the vicinity through the weekend. Monsoonal moisture will linger across the Four Corners area where locally heavy downpours will be possible through early next week. Meanwhile, triple-digit heat is forecast for the interior sections of the Pacific Northwest into the Intermountain region as well as interior California through the weekend, as cool air filters into the northern Plains behind the second cold front. Given the better than average agreement in the latest guidance, the latest WPC forecast blend utilized a majority weight of operational models (18Z GFS and 12Z ECMWF/CMC) versus 18Z GEFS/ECMWF means through day 5 Fri and then trended toward an even model/ensemble blend among GFS/ECMWF runs and their means. Kong WPC medium range 500 mb heights, surface systems, weather grids, quantitative precipitation, winter weather outlook probabilities and heat indexes are found at: http://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif http://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif http://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html http://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml http://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4 http://www.wpc.ncep.noaa.gov/heat_index.shtml